U.S. patent application number 11/848862 was filed with the patent office on 2008-03-06 for broad band antenna.
This patent application is currently assigned to SAMSUNG ELECTRO-MECHANICS CO., LTD.. Invention is credited to Seok Bae, In Young KIM.
Application Number | 20080055178 11/848862 |
Document ID | / |
Family ID | 39150742 |
Filed Date | 2008-03-06 |
United States Patent
Application |
20080055178 |
Kind Code |
A1 |
KIM; In Young ; et
al. |
March 6, 2008 |
BROAD BAND ANTENNA
Abstract
A broad band antenna including: a body formed of a material
having a relative permittivity of 2 to 20, a relative permeability
of 1 to 10, and a magnetic loss tangent of 0.001 to 0.2, at a
usable frequency; and at least one radiator disposed on the body.
The material forming the body may be a composite material formed of
a polymer resin mixed with a magnetic powder. The composite
material may contain the magnetic powder by 90 wt % with respect to
a total weight.
Inventors: |
KIM; In Young; (Gyunggi-do,
KR) ; Bae; Seok; (Gyunggi-do, KR) |
Correspondence
Address: |
LOWE HAUPTMAN HAM & BERNER, LLP
1700 DIAGONAL ROAD
SUITE 300
ALEXANDRIA
VA
22314
US
|
Assignee: |
SAMSUNG ELECTRO-MECHANICS CO.,
LTD.
GYUNGGI-DO
KR
|
Family ID: |
39150742 |
Appl. No.: |
11/848862 |
Filed: |
August 31, 2007 |
Current U.S.
Class: |
343/787 |
Current CPC
Class: |
H01Q 1/38 20130101; H01Q
9/40 20130101 |
Class at
Publication: |
343/787 |
International
Class: |
H01Q 1/00 20060101
H01Q001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 4, 2006 |
KR |
10-2006-84698 |
Claims
1. A broad band antenna comprising: a body formed of a material
having a relative permittivity of 2 to 20, a relative permeability
of 1 to 10, and a magnetic loss tangent of 0.001 to 0.2, at a
usable frequency; and at least one radiator disposed on the
body.
2. The broad band antenna of claim 1, wherein the material forming
the body is a composite material formed of a polymer resin mixed
with a magnetic powder.
3. The broad band antenna of claim 2, wherein the composite
material contains the magnetic powder by 90 wt % with respect to a
total weight.
4. The broad band antenna of claim 2, wherein the magnetic powder
comprises a magnetic substance having at least one element selected
from Fe, Ni, Co, Mn, Mg, Ba, Sr and Zn.
5. The broad band antenna of claim 4, wherein the magnetic powder
comprises at least one selected from carbonyl iron, a Ba ferrite, a
NiZn ferrite and a MnZn ferrite.
6. The broad band antenna of claim 5, wherein the magnetic powder
is the carbonyl iron and the composite material contains the
magnetic powder by 45 to 85 wt % with respect to a total
weight.
7. The broad band antenna of claim 5, wherein the magnetic powder
is the NiZn ferrite and the composite material contains the
magnetic powder by 45 to 90 wt % with respect to a total
weight.
8. The broad band antenna of claim 5, wherein the magnetic powder
is the Ba ferrite and the composite material contains the magnetic
powder by 50 to 87.5 wt % with respect to a total weight.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the priority of Korean Patent
Application No. 2006-84698 filed on Sep. 4, 2006, in the Korean
Intellectual Property Office, the disclosure of which is
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a broad band antenna, more
particularly, which can be miniaturized using a magnetic substance
without considerable decline in gain.
[0004] 2. Description of the Related Art
[0005] Of late, a broadcasting service is provided to a mobile
telecommunication terminal or information is transmitted wirelessly
between a personal computer and a terminal, or between terminals.
That is, wireless telecommunication has been commonly available.
Also, diversity in information has led to a broader band of a
usable frequency employed in telecommunication between devices.
With this trend, broadband characteristics of an antenna have
gained importance.
[0006] A representative example of a broad band antenna currently
manufactured includes a helical antenna, a spiral antenna and a log
periodic antenna. In order to realize a compact broad band antenna,
bandwidth may be increased by applying a log periodic design to a
patch antenna or utilizing a multilayer structure. Also,
multi-resonance may be generated by a planar inverted F antenna
(PIFA). Alternatively, an antenna may be switch-connected to be
adjusted in a band, which is however not suited to the small-sized
antenna due to decrease in gain.
[0007] Especially, a terrestrial broadcasting antenna for a mobile
telecommunication terminal has a usable frequency band of 200 to
750 MHz, which is lower than a typical communication frequency. But
the antenna has a size proportional to a wavelength of a usable
frequency. Thus, with decrease in the usable frequency, the antenna
is sized bigger. But the antenna with bigger size does not serve
its purpose as a part of a mobile telecommunication terminal. On
the contrary, the antenna with smaller size may be degraded in gain
or bandwidth. Therefore, it is crucial to implement a compact broad
band antenna at a relatively low frequency band.
[0008] As described above, the currently needed antenna
characteristics can be hardly achieved only with structural changes
in design. In the art, a new approach for addressing this
technological issue has been called for.
SUMMARY OF THE INVENTION
[0009] An aspect of the present invention provides a novel broad
band antenna which can be miniaturized using a magnetic substance
and controlled in magnetic loss of an antenna body, thereby
attaining broadband characteristics without a big decrease in
gain.
[0010] According to an aspect of the present invention, there is
provided a broad band antenna including: a body formed of a
material having a relative permittivity of 2 to 20, a relative
permeability of 1 to 10, and a magnetic loss tangent of 0.001 to
0.2, at a usable frequency; and at least one radiator disposed on
the body.
[0011] The material forming the body may be a composite material
formed of a polymer resin mixed with a magnetic powder. The
composite material may contain the magnetic powder by 90 wt % with
respect to a total weight.
[0012] The magnetic powder may be a magnetic substance having at
least one element selected from Fe, Ni, Co, Mn, Mg, Ba, Sr and Zn.
The magnetic powder may be at least one selected from carbonyl
iron, a Ba ferrite, a NiZn ferrite and a MnZn ferrite.
[0013] The magnetic powder may be the carbonyl iron and the
composite material may contain the magnetic powder by 45 to 85 wt %
with respect to a total weight.
[0014] The magnetic powder may be the NiZn ferrite and the
composite material may contain the magnetic powder by 45 to 90 wt %
with respect to a total weight.
[0015] The magnetic powder may be the Ba ferrite and the composite
material may contain the magnetic powder by 50 to 87.5 wt % with
respect to a total weight.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The above and other aspects, features and other advantages
of the present invention will be more clearly understood from the
following detailed description taken in conjunction with the
accompanying drawings, in which:
[0017] FIG. 1 illustrates a sample of an antenna structure for
evaluating a material forming a broad band antenna body, applicable
according to an exemplary embodiment of the invention;
[0018] FIGS. 2A and 2B are graphs illustrating dielectric
properties and magnetic properties of a body-forming material
applicable to a broad band antenna, respectively, according to an
exemplary embodiment of the invention;
[0019] FIG. 3 is a perspective view illustrating an antenna
structure employed in first to third examples of the present
invention;
[0020] FIG. 4 is a graph illustrating frequency characteristics of
a broad band antenna formed of a composite material containing
carbonyl iron according to the first example of the present
invention;
[0021] FIGS. 5A and 5B are graphs illustrating frequency
characteristics of a broad band antenna formed of a composite
material containing a NiZn ferrite and gain characteristics
adjusted by a matching circuit, respectively, according to the
second example of the present invention; and
[0022] FIGS. 6A and 6B are graphs illustrating frequency
characteristics of a broad band antenna formed of a Ba ferrite and
gain characteristics adjusted by a matching circuit, respectively,
according to the third example of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0023] According to the present invention, a magnetic substance is
at least partially applied to an antenna body to utilize both
permittivity and permeability, thereby more easily producing a
smaller antenna. Hereinafter, a detailed description will be given
based on following Equations. .lamda. = .lamda. 0 .mu. Equation
.times. .times. 1 ##EQU1##
[0024] where .lamda. is a wavelength of an actual frequency,
.lamda..sub.0 is a wavelength determined by a radiator, .di-elect
cons. is relative permittivity of the body and .mu. is relative
permeability of the body. As noted in Equation 1, a wavelength of a
final frequency is inversely proportional to permittivity and
permeability. Therefore, the wavelength of the final frequency can
be further shortened by utilizing permittivity and permeability as
well.
[0025] Particularly, as shown in Equation 2 below, a wavelength
impedance .eta. of the body is increased with increase in
permittivity. This causes a field to be confined inside the
material and lowers gain of the antenna. Here, .eta..sub.0 is a
wavelength impedance in a free space. .eta. = .eta. 0 .times. .mu.
Equation .times. .times. 2 ##EQU2##
[0026] Also, increase only in permittivity leads to decrease in
bandwidth of the antenna, thus considerably hampering design of a
broad band antenna. As described above, the permittivity, when
employed alone, may be disadvantageous for antenna
characteristics.
[0027] As described above, according to the present invention, the
antenna is reduced in size and improved in gain by using both
permittivity and permeability. Furthermore, according to the
present invention, magnetic loss of the body is controlled to
increase bandwidth of the antenna, without significantly
undermining radiation efficiency.
[0028] The antenna bandwidth is governed by a quality factor Q
according to following Equation 3: FBW[%]=.DELTA.f/f=1/Q Equation
3
[0029] The Q value is determined by loss of the antenna radiator,
dielectric loss and magnetic loss. According to the present
invention, a magnetic substance is adopted and magnetic loss of a
body-forming material is used to design a smaller broad band
antenna without a decrease in gain and radiation efficiency.
[0030] Through repeated experiments (refer to first embodiment)
based on the aforesaid novel concept, the inventors propose that an
antenna body with at least one radiator disposed thereon be formed
of a material having a relative permittivity of 2 to 20, a relative
permeability of 1 to 10, and a magnetic loss tangent of 0.001 to
0.2, at a usable frequency. The magnetic loss tangent may be
adequately increased to noticeably improve bandwidth of the antenna
without addition of size. However, the magnetic loss tangent
greater than 0.2 may degrade radiation efficiency excessively.
[0031] The body-forming material satisfying the aforesaid
conditions according to the present invention may be easily
manufactured by filling a magnetic powder, with a polymer resin as
a matrix. In general, the magnetic substance obtained by sintering
is one of ceramic materials and thus greatly brittle. Especially,
the magnetic substance, when applied to a mobile telecommunication
terminal, may not satisfy a reliability condition such as a drop
test. However, a composite material having the magnetic powder
filled in the polymer resin may solve such a problem.
[0032] Hereinafter, the present invention will be described in
detail by way of embodiments.
Example 1
[0033] In first example, antennas were manufactured with materials
satisfying permittivity, permeability and magnetic loss
characteristics. Then, radiation efficiency, bandwidth and a size
reduction ratio of the antennas were measured to confirm
improvement effects according to the present embodiment.
[0034] In the first example, body-forming materials were
constructed to carry maximum properties to identify subsequent
effects therefrom. The first example adopted as a basic model a
monopol antenna including a rectangular parallelepiped block 11
(L.times.W.times.T=73.times.4.times.4 cm) surrounding a radiator,
i.e., Cu conductive line 12. Then, the body-forming materials noted
in Table 1 were prepared to be manufactured into respective
rectangular parallelepiped blocks and then antennas each satisfying
a central frequency band of 520 MHz.
[0035] As seen in Table 1, composite materials of dielectric and
magnetic substances or sintered magnetic substances employed in
Inventive Examples 1 to 6 satisfy permittivity, permeability and
magnetic loss tangent of the present embodiment. Comparative
Example 1 employed an antenna in the form of only a Cu conductive
line without a body, i.e., the Cu conductive line in air, to have a
central frequency of 520 MHz. In Comparative Example 2, a body was
manufactured using FR4, a chief material for a conventional printed
circuit board. TABLE-US-00001 TABLE 1 Dielec- Permit- Perme- tric
Magnet- Body-forming tivity ability loss ic loss material
(.epsilon.) (.mu.) (tan .delta..sub..epsilon.) (tan
.delta..sub..mu.) Inventive 1 Carbonyl iron 4.7 1.7 0.044 0.161 (50
wt %) + silicone resin Inventive 2 Carbonyl iron 7.9 2.8 0.040
0.144 (75 wt %) + silicone resin Inventive 3 Carbonyl iron 9.9 3.5
0.066 0.140 (83.3 wt %) + silicone resin Inventive 4 Carbonyl iron
12.5 4.2 0.081 0.142 (87.5 wt %) + silicone resin Inventive 5
M-type Ba 5.6 1.2 0.039 0.155 ferrite (50 wt %) + silicone resin
Inventive 6 NiZn ferrite 11 7 0.001 0.040 pellet Comparative Air 1
1 0 0 1 Comparative FR4 4.4 1 0.01 0 2
[0036] More specifically, according to Inventive Examples 1 to 4,
to manufacture the antenna, carbonyl iron was mixed with a silicone
resin by 50 wt %, 75 wt %, 83.3 wt %, and 87.5 wt % with respect to
a total weight of each of the body-forming materials, respectively.
Here, a small amount of dispersant and superplasticizer were also
used. In Inventive Example 5, a M-type Ba ferrite was mixed with a
silicone resin by about 50 wt % to produce an antenna similar to
Inventive Examples 1 to 4. In Inventive Example 6, a NiZn ferrite
pellet was employed, unlike the aforesaid composite material.
[0037] Antennas having bodies formed of the materials noted in
Table 1 above, were manufactured to measure radiation efficiency,
bandwidth and a size reduction ratio thereof. The antennas
exhibited a bandwidth with a voltage standing wave ratio (VSWR) of
3 or less. The size reduction ratio was measured by determining a
ratio of a length l of each conductive line with respect to a
length of the antenna in the form of a Cu conductive line in air.
The results are shown in Table 2. TABLE-US-00002 TABLE 2 Size
Radiation reduction efficiency ratio (n, %) (%) Bandwidth (MHz)
Inventive 1 90.27 68.06 55.70 Inventive 2 79.02 62.83 67.00
Inventive 3 70.77 56.54 65.10 Inventive 4 60.47 49.21 80.50
Inventive 5 96.37 76.44 59.35 Inventive 6 94.21 58.12 48.10
Comparative 1 96.82 100 83.00 Comparative 2 95.08 76.44 51.90
[0038] The antenna of Inventive Example 6 utilizing a sintered
magnetic substance was slightly decreased in bandwidth. Meanwhile,
the antennas of Inventive Examples 1 to 5 showed a broad bandwidth
of about 55 MHz or more, even 80 MHz or more. The antennas of
Inventive Examples 1 to 5 also exhibited a high size reduction
ratio of 30% or more, and even 50% or more. This confirms that the
materials satisfying conditions of the present invention, when used
to form the body of the antenna, assure a miniaturizable broad band
antenna.
[0039] Here, the antennas of Inventive Examples were slightly
lowered in radiation efficiency. However, as shown in FIG. 1, the
measurement was designed to evaluate characteristics of the
body-forming materials, and thus the materials were constructed to
fully surround the radiator 12. Therefore, the modest decrease in
radiation efficiency is insignificant since higher radiation
efficiency is expected from an actually implemented antenna
structure, i.e., an antenna having a radiator disposed on a surface
of a body.
[0040] As described above, according to Inventive Examples,
magnetic loss is adequately controlled under proper conditions of
permittivity and permeability. In consequence, it has been
confirmed that this increases bandwidth while not significantly
degrading radiation efficiency, and also noticeably reduces size of
the antenna.
[0041] The body-forming material applicable to the present
embodiment may have a magnetic loss tangent of 0.001 to 0.2 under
the permittivity and permeability conditions as described above.
Accordingly, the body-forming material may adopt a sintered
magnetic substance satisfying the permittivity, permeability and
magnetic loss conditions.
[0042] Particularly, the body-forming material may utilize a soft
magnetic composite material having a magnetic substance and a
polymer resin mixed therein to enhance mechanical reliability and
easily design desired dielectric properties and magnetic
conditions. A magnetic powder applicable to the present embodiment
may be a magnetic substance having at least one element selected
from Fe, Ni, Co, Mn, Mg, Ba, Sr and Zn. One of carbonyl iron, a Ba
ferrite, a NiZn ferrite and a MnZn ferrite may be utilized more
beneficially for the magnetic powder.
[0043] FIGS. 2A and 2B are graphs illustrating dielectric
properties and magnetic properties of various soft composite
materials mixed with various types of magnetic powder,
respectively. Here, a silicone resin is used as a polymer
resin.
[0044] As shown in FIGS. 2A and 2B, the soft magnetic composite
materials are varied slightly in dielectric loss according to
permittivity but varied very greatly in magnetic loss according to
permeability. Therefore, according to the present embodiment,
magnetic loss serves more for controlling the antenna
characteristics than dielectric loss. Also, as shown in FIGS. 2A
and 2B, various types of magnetic powder such as a magnetic metal
powder or a ferrite powder can satisfy conditions of the present
embodiment.
[0045] Frequency characteristics of an antenna will be described by
way of second to fourth examples.
[0046] As shown in FIG. 3, each of antennas employed in the
examples below is structured such that a radiator is disposed on a
surface of a body in the form of a rectangular parallelepiped
block.
[0047] A broad band antenna structure 20 used in the examples below
will be described roughly with reference to FIG. 3. The broad band
antenna structure 20 includes a body 21, and a first radiation
pattern 22 and second radiation patterns 24a and 24b formed on
opposing sides of the body 21, respectively. The first radiation
pattern 22 and the second radiation patterns 24a and 24b are
connected together to function as a single radiation pattern. The
first radiation pattern 12 includes a tapered slot opened at one
side and has four pairs of log periodic patterns 16a and 16b.
[0048] The second and third examples adopt antennas structured in
FIG. 3. Various frequency characteristics other than size reduction
and bandwidth increase described in the first example were measured
to identify actual applicability of the antennas. In fact,
frequency characteristics may be complicated depending on
permittivity and permeability. This is because with higher
permittivity and permeability, a Q value increases but may
potentially decrease due to increase in loss.
[0049] Therefore, appropriate permittivity and permeability should
be selected as in the aforesaid conditions of the present example.
Under the conditions of the present example, adequate gain may be
obtained at a usable frequency band or gain may be increased to a
desired level by a matching circuit. This will be confirmed by
examples below.
Example 2
[0050] In second example, carbonyl iron powder and a silicon resins
were mixed at adequate ratios to prepare soft magnetic composite
materials used in antenna bodies (40.times.10.times.2.5 mm).
[0051] That is, the carbonyl iron powder and the silicone resin
were mixed at a ratio of 1:1(C1), 3:1(C2), and 5:1(C3),
respectively. The carbonyl iron powder was added by 50 wt %, 66.5
wt %, and 83.3 wt % with respect to a total weight of each of the
soft magnetic composite materials.
[0052] Similarly to the results of Example 1, a higher ratio of the
carbonyl iron powder increased permittivity and permeability
(magnetic loss), thereby leading to a low band frequency, i.e.,
size reduction effects.
[0053] In antennas manufactured according to the second example,
VSWR and gain thereof are influenced by not only magnetic loss of
the materials but also permittivity and permeability and thus shown
a bit complicated. The antennas exhibit somewhat high gain at a
usable frequency band with a VSWR of 3 or less.
[0054] Considering the results of the second example and
characteristic differences among magnetic substances, in a case
where carbonyl iron is employed as a magnetic powder, the composite
material may contain the magnetic powder by 45 to 85 wt % with
respect to a total weight.
Example 3
[0055] In third example, a NiZn ferrite powder and a silicone resin
were mixed at adequate ratios to prepare soft magnetic composite
materials used in antenna bodies (40.times.10.times.2.5 mm).
[0056] That is, the NiZn ferrite powder and the silicone resin were
mixed at a ratio of 3:1(N1), 5:1(N2), 7:1(N3), and 9:1(N4),
respectively. When converted into weight percent, the NiZn ferrite
powder is construed to be added at a varying ratio of 50 wt % to 90
wt %.
[0057] In general, the NiZn ferrite powder has a magnetic loss
tangent higher than those of other magnetic powders, e.g., carbonyl
iron, thus expected to be limited in its use. Meanwhile, in a case
where the NiZn ferrite powder is mixed with the silicone resin of
polymer into the soft magnetic composite materials to be applied to
antennas as designed in FIG. 3, the antennas exhibit relatively
lower gain as shown in FIG. 5A.
[0058] However, this low level can be improved to a desired level
by a simple matching circuit. Therefore, the antennas of the third
example may be beneficially employed in a mobile telecommunication
terminal.
[0059] Considering results of the third example and characteristic
differences among magnetic substances, in a case where the NiZn
ferrite is used as a magnetic powder, the composite material may
contain the magnetic powder by 45 to 90 wt % with respect to a
total weight.
Example 4
[0060] In fourth example, a Z-type Ba ferrite and a silicone resin
were mixed at adequate ratios to prepare soft magnetic composite
materials used in antenna bodies (40.times.10.times.2.5 mm).
[0061] That is, the Z-type Ba ferrite powder and the silicone resin
were mixed at a ratio of 3:1(Z1), 5:1(Z2), and 7:1(Z3),
respectively. When converted into weight percent, the Z type Ba
ferrite powder is construed to be added at a varying ratio of 50 wt
% to 87.5 wt %.
[0062] In general, the Z type Ba ferrite powder is lower in
permittivity and permeability than other magnetic powders, e.g.
carbonyl iron, thus low in a magnetic loss tangent. Therefore, the
Z type Ba ferrite powder may be less effective than other magnetic
powders in terms of miniaturization or lower band frequency.
However, very high temperature stability of the Z type Ba ferrite
powder may serve to significantly improve reliability.
[0063] In a similar manner to the third example, as shown in FIG.
6A, antennas of the fourth example demonstrate relatively lower
gain. But this low level can be improved to a desired level by a
simple matching circuit as shown in FIG. 6B.
[0064] Considering results of the fourth example and characteristic
differences among magnetic substances, in a case where the Ba
ferrite is used as a magnetic powder, the composite material may
contain the magnetic powder by 50 to 87.5 wt % with respect to a
total weight.
[0065] Particularly, in a case where the Ba ferrite is used for the
soft magnetic composite material, an upper limit of a mixing ratio
of the magnetic powder is understood to be set to a level where
radiation properties are not degraded by increase in electrical
conductivity of the antenna body.
[0066] As set forth above, according to exemplary embodiments of
the invention, a magnetic substance is employed to realize a
smaller antenna. Also, magnetic loss of the antenna is controlled
without a big decrease in gain to attain broadband characteristics.
This assures a commercially viable smaller-sized antenna having
broadband characteristics at a low frequency band.
[0067] While the present invention has been shown and described in
connection with the exemplary embodiments, it will be apparent to
those skilled in the art that modifications and variations can be
made without departing from the spirit and scope of the invention
as defined by the appended claims.
* * * * *